US4176345A - Reflecting electrostatic display cell - Google Patents

Reflecting electrostatic display cell Download PDF

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Publication number
US4176345A
US4176345A US05/866,340 US86634078A US4176345A US 4176345 A US4176345 A US 4176345A US 86634078 A US86634078 A US 86634078A US 4176345 A US4176345 A US 4176345A
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United States
Prior art keywords
display cell
recited
electret
dihedral
electrodes
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Expired - Lifetime
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US05/866,340
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English (en)
Inventor
Francois Micheron
Jean-Luc Bruneel
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Thales SA
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Thomson CSF SA
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
    • H02N1/00—Electrostatic generators or motors using a solid moving electrostatic charge carrier
    • H02N1/002—Electrostatic motors
    • H02N1/006—Electrostatic motors of the gap-closing type
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
    • G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
    • G09F9/37—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements being movable elements
    • G09F9/372—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements being movable elements the positions of the elements being controlled by the application of an electric field

Definitions

  • the invention relates to electrostatic display cells for constructing unit elements which can assume one of two stable, visually distinct states under the action of a temporary electric signal.
  • the cells can be assembled to form display devices having all desired shapes.
  • bistable display devices comprising a sheet mounted on a pivot and provided with a permanent magnet.
  • An electromagnet acts on the permanent magnet and pivots the sheet, bringing it into one of two stable positions. The sheet remains in position after the electromagnet is deenergized.
  • the device uses up considerable energy at each switch-over.
  • a display device comprising a sheet of aluminum-coated plastics which winds around a circular cylindrical electrode when a voltage is applied between the sheet and the electrode.
  • the appearance of the device varies depending on whether the sheet is rolled around the electrode or not.
  • the current consumption is very low but is continuous in one of the states.
  • dielectric materials bearing permanent electric charges are usually in the form of thin colorless transparent flexible sheets made of a plastics having very high resistivity, e.g. polypropylene.
  • the sheets are permanently charged, e.g. by subjecting them to a corona discharge or implanting ions or electrons, using a particle accelerator.
  • the charges thus implanted in the materials are secured therein for a very long period (e.g. 100 years) owing to its very high resistivity.
  • a reflecting electrostatic display cell for presenting under the control of an external temporary electric control signal two stable configurations, said cell comprising:
  • FIG. 1 illustrates a display cell according to the invention
  • FIGS. 2 and 3 diagrammatically illustrate the active parts of said cell in its two separate and distinct stable states
  • FIGS. 4, 5 and 6 illustrate cross-sections through a composite electret sheet
  • FIGS. 7 and 8 diagrammatically illustrate matrix control systems
  • FIGS. 9 and 10 diagrammatically illustrate a particular display device.
  • FIG. 1 illustrates a cell comprising a base 101, a dihedral block 102, a sheet of electret 103, two electrodes 104, and 105, two connections 106 and 107, two terminals 108 and 109, a glass plate 110, columns 111 and nuts 112.
  • the dihedral block 102 is secured to the base 101 and has a dihedral notch, the dihedral angle being approximately 90° in the described example, on the side remote from the holder and facing glass 110, the incident light D and the observer's eye ⁇ .
  • a slot F is formed in block 102 and extends inwards from the dihedral edge. It is used to secure the electret sheet 103 in a substantially central position (when the sheet is not bent) relative to the dihedral angle. Slot F is just wide enough to slide in the electret, which is secured with a drop of glue (not shown).
  • Block 102 is not conductive and bears electrodes 104 and 105, one electrode being disposed on each dihedral surface. Electrodes 104 and 105 are connected to terminals 108 and 109 respectively by conductors 106 and 107, which are shown detached from the block in order to simplify the drawing, but can be stuck to the lateral surfaces or extend through internal apertures.
  • Electrodes 104 and 105 the electrodes are made of a conducting paint having a first color A for electrode 104 and a second and different color B for electrode 105. Since the control current is extremely small (a few tens of nA's ) the resistivity of the electrodes can be high, so that a large number of different colors can be chosen, since the quality and the proportion of the conducting agent are of little importance. Other embodiments are possible, e.g. a layer of paint covered with a transparent electrode.
  • electret 103 tends to stick to a surface of the dihedron.
  • the electret is painted with a different color on each surface, preferably the same colors as the facing electrodes.
  • the surface facing electrode 104 is painted with color A and the surface facing electrode 105 is painted with color B.
  • the observer ⁇ sees the dihedron reflecting a uniform color A.
  • the electrode sticks against surface 104, the observer sees the dihedral blocking reflecting a uniform color B.
  • the device which operates by electrostatic means, is sensitive to various external agents such as dust which may accumulate thereon.
  • the glass plate 110 secured to base 101 by columns 111 and nuts 112 gives protection in co-operation with a lateral cap system (not shown) which is used when the device is used by itself, without adjacent cells.
  • FIG. 2 diagrammatically shows one of the two stable states of the cell shown in FIG. 1, whereas FIG. 3 shows the other stable state.
  • no external voltage is necessary. If electret 103 is negatively charged (as in the drawing) it induces a positive surface layer in the electrode against which it sticks, and a deeper negative layer in the same electrode, the negative layer being necessary in order to maintain the electric neutrality of the conductor, which is not connected to an external source of voltage.
  • Electrode 104 can assume a similar charge pattern to that of electrode 105. In order to change from one state to the other, the electret must be released from one electrode and attracted by the other. To this end, a voltage supply is connected between the electrodes via terminals 108 and 109 so that, in the case of a negative electret, the electrode to which electret 103 adheres is charged negatively whereas the other electrode is charged positively.
  • a particularly interesting dihedral angle is 180°, i.e. a flat structure which is the most clearly visible, more particularly at high incidence angles.
  • the control voltage is 3000 V, so that transistors cannot be used in the present state of technology.
  • the first method is to reduce the bending forces at the fold in the electret.
  • the sheet of electret is made thinner at the fold, as shown by groove P in FIG. 1. It can be made thinner, e.g. by locally heating the plastics with a resistive wire through which an electric current flows, and by pulling the electret.
  • the resulting contraction in cross-section can exceed 300% before breakage, and the thus-formed pivot has a negligible torque but is very long-lasting.
  • the second method is to distribute the charges in non-uniform manner in the electret, since the electret should advantageously come loose from the electrode surface when all points have substantially the same voltage.
  • a dihedral block comprising two electrodes behaves like a capacitor in which the electric field decreases from the edge outwardly in proportion to 1/r. Consequently, if the forces acting on the electret are to be uniform at every point, the charge distribution must increase from the edge outwardly in linear manner.
  • the electrodes begin at 1 mm from the dihedral edge (they must in any case start at a limited distance in order to avoid an excessive field), the resulting charge density increase from 10 -10 C/cm 2 at 1 mm from the edge to 10 -9 C/cm 2 at 1 cm from the edge.
  • This range of variation is quite practicable since the top value is limited to approx. 10 -8 C/cm 2 owing to neutralization by the free charges of the electret and the bottom value is limited to approx. 10 -11 C/cm 2 owing to the low reproducibility due to stray charges before the electret charging operation.
  • Various methods are used to obtain the aforementioned linear distribution.
  • the electret can be given a corona discharge via a plurality of pins which number of pins increases towards the region where the charge must be highest; the approximation is rough but sufficient.
  • the electret can be charged by direct implantation of ions or electrons, using, e.g. an electronic masking apparatus. In such an apparatus the flux of charges can be adjusted, the main methods for this being action on the beam intensity or on the duration of scanning. The resulting distribution can be much closer to the optimum distribution than when the corona effect is used.
  • Another method includes preventing the electret from sticking on the electrode and keeping it at a distance of a few microns (approx. 10-20) therefrom.
  • shims are disposed between the electret and the electrode.
  • the shims may advantageously be formed on the electrode itself, which then has the shape of a grid.
  • the spacing is produced by using a dielectric layer having high permittivity.
  • the resulting modification in the electric field reduces the force of attraction between the electret and the electrode and correspondingly reduces the control voltage.
  • the average charge on the electret can be reduced while retaining a local charge between 10 -9 and 10 -10 C/cm 2 , by producing a pattern, preferably by direct implantation, the pattern comprising charged regions and non-charged regions.
  • the electret should have two differently colored surfaces. It is very difficult to paint an electret, particularly to paint both surfaces simultaneously, since the solvent in the paint tends to dissolve the surface layer containing the charges, which are thus neutralized. Thus a solvent inert towards the electret material must be used and the resistivity of the pigments must be selected so as not to decrease the resistivity of the electret.
  • FIG. 4 shows a structure of the kind in question, comprising two electret sheets 41, 42 and two layers of paint A and B.
  • an intermediate sheet 43 is painted and the electrets are secured thereto.
  • the intermediate sheet is naturally colored or reflecting, e.g. in the case of a metal sheet, and requires only one layer of paint.
  • the resulting display cell can have various shapes when seen from the front. Two particular shapes (the square and the rectangle) can be used to construct display devices having complex shapes, wherein the elementary units are a set of preferably identical cells.
  • an alpha-numerical display it is known that all the Roman letters and the arabic figures can be made up from a matrix having seven lines each including five squares. In this manner, an alpha-numerical display unit can be constructed from 35 square display cells each cell according to the invention. Another, more aesthetic method involves a matrix of 9 lines and 7 columns, i.e. 63 cells.
  • the matrix can be controlled cell by cell, using two connections per cell, but the number of connections can be reduced by a matrix control system, a small-scale example of which is shown in FIG. 7.
  • Points A, B, C, D represent the cells arranged in two columns V 1 , V 2 and two lines H 1 , H 2 .
  • Two voltages sources are required, i.e. +V/2 and -V/2 (these being the cell control voltage).
  • the voltage +V/2 is applied to line H 2 and the voltage -V/2 is applied to line V 1 in accordance with the desired position.
  • cell C is acted upon by voltage V and changes state.
  • Cells A and D are subjected to voltages having the absolute value V/2, and cell B is not subjected to any voltage. Consequently, cells A, B and D do not change state.
  • FIG. 8 Another control system, shown in FIG. 8, includes non-switched cells subjected to a voltage having an absolute value of only V/3. This allows a wider scatter in the control voltages of the various cells, resulting in less narrow manufacturing tolerances. As FIG. 8 shows, only cell C is subjected to voltage V, whereas the three other cells are subjected to a voltage having an absolute value V/3.
  • the invention is not limited to displaying two colors, but can be used for displaying any two structures which can be visually distinguished, e.g. a reflecting surface as opposed to a black surface or a pattern which is different for each state.
  • FIGS. 9 and 10 are plan views based on the last-mentioned feature, showing a device for displaying the state of a cutoff means, e.g. a valve in a synoptic control board of a refinery.
  • FIG. 9 shows a device comprising an electrode 81 on the left and an electrode 82 covered with an electret 83 on the right.
  • the shaded regions 84, 85 outside the device form part of the synoptic board.
  • the valve is symbolically shown in the open state, by means of the shaded strip 86, 87 drawn on electrode 81 and on one surface of electret 83.
  • FIG. 10 shows the same device in its other stable state, wherein electrode 83 covers electrode 81.
  • the shaded strips 88, 89 on the other surface of electret 83 and on electrode 82 symbolically represent the closed position of the valve.
US05/866,340 1977-01-04 1978-01-03 Reflecting electrostatic display cell Expired - Lifetime US4176345A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR7700077 1977-01-04
FR7700077A FR2376477A1 (fr) 1977-01-04 1977-01-04 Cellule d'affichage electrostatique et dispositif d'affichage comprenant une telle cellule

Publications (1)

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US4176345A true US4176345A (en) 1979-11-27

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US05/866,340 Expired - Lifetime US4176345A (en) 1977-01-04 1978-01-03 Reflecting electrostatic display cell

Country Status (6)

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US (1) US4176345A (fr)
JP (1) JPS53111292A (fr)
DE (1) DE2800341A1 (fr)
FR (1) FR2376477A1 (fr)
GB (1) GB1593011A (fr)
IT (1) IT1101905B (fr)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0048261A1 (fr) * 1980-03-24 1982-03-31 Black & Decker Inc. Outil electrique commande par micro-ordinateur
US4818877A (en) * 1986-02-28 1989-04-04 Thomson-Csf Memory display system
US4825205A (en) * 1987-06-19 1989-04-25 Lee Gyu S Changeable display unit for use in a sign device
US5627374A (en) * 1994-11-18 1997-05-06 Thomson-Csf Static infrared panoramic watching device with multiple matrix detectors
US5950237A (en) * 1996-06-28 1999-09-14 Thomson-Csf Jacket for the personal protection of an infantryman
US6031656A (en) * 1998-10-28 2000-02-29 Memsolutions, Inc. Beam-addressed micromirror direct view display
US6034807A (en) * 1998-10-28 2000-03-07 Memsolutions, Inc. Bistable paper white direct view display
US6427910B1 (en) * 1999-12-17 2002-08-06 International Business Machines Corporation Method for managing and updating overloaded cards
US6639572B1 (en) 1998-10-28 2003-10-28 Intel Corporation Paper white direct view display
US20040263936A1 (en) * 2003-04-15 2004-12-30 Takeshi Nanjyo Optical deflection apparatus and manufacturing method thereof, optical deflection array, imaging apparatus, and image projection display apparatus
US6924792B1 (en) 2000-03-10 2005-08-02 Richard V. Jessop Electrowetting and electrostatic screen display systems, colour displays and transmission means
US7463398B2 (en) 2002-02-19 2008-12-09 Liquivista B.V. Display device
US8508436B2 (en) 2005-09-28 2013-08-13 Intellectual Properties | Kft Electronic display systems

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH641315B (fr) * 1981-07-02 Centre Electron Horloger Dispositif d'affichage miniature a volets.
NL8402038A (nl) * 1984-06-28 1986-01-16 Philips Nv Elektroskopische beeldweergeefinrichting.

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3648281A (en) * 1969-12-30 1972-03-07 Ibm Electrostatic display panel

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3648281A (en) * 1969-12-30 1972-03-07 Ibm Electrostatic display panel

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0048261A1 (fr) * 1980-03-24 1982-03-31 Black & Decker Inc. Outil electrique commande par micro-ordinateur
EP0048261A4 (fr) * 1980-03-24 1982-07-19 Black & Decker Inc Outil electrique commande par micro-ordinateur.
US4818877A (en) * 1986-02-28 1989-04-04 Thomson-Csf Memory display system
US4825205A (en) * 1987-06-19 1989-04-25 Lee Gyu S Changeable display unit for use in a sign device
US5627374A (en) * 1994-11-18 1997-05-06 Thomson-Csf Static infrared panoramic watching device with multiple matrix detectors
US5950237A (en) * 1996-06-28 1999-09-14 Thomson-Csf Jacket for the personal protection of an infantryman
US6031656A (en) * 1998-10-28 2000-02-29 Memsolutions, Inc. Beam-addressed micromirror direct view display
US6034807A (en) * 1998-10-28 2000-03-07 Memsolutions, Inc. Bistable paper white direct view display
US6639572B1 (en) 1998-10-28 2003-10-28 Intel Corporation Paper white direct view display
US6427910B1 (en) * 1999-12-17 2002-08-06 International Business Machines Corporation Method for managing and updating overloaded cards
US8963819B2 (en) 2000-03-10 2015-02-24 Intellectual Properties I Kft. Light modulating display device using electrowetting effect
US6924792B1 (en) 2000-03-10 2005-08-02 Richard V. Jessop Electrowetting and electrostatic screen display systems, colour displays and transmission means
US20080261661A1 (en) * 2000-03-10 2008-10-23 Jessop Richard V Mobile telephone devices
US20080231574A1 (en) * 2000-03-10 2008-09-25 Jessop Richard V Light modulating display device using electrowetting effect
US7463398B2 (en) 2002-02-19 2008-12-09 Liquivista B.V. Display device
US7898718B2 (en) 2002-02-19 2011-03-01 Liquavista B.V. Display device
US20110116153A1 (en) * 2002-02-19 2011-05-19 Liquavista B.V. Display device
US8213071B2 (en) 2002-02-19 2012-07-03 Samsung Lcd Netherlands R & D Center B.V. Display device
US7113321B2 (en) * 2003-04-15 2006-09-26 Ricoh Company, Ltd. Optical deflection apparatus and manufacturing method thereof, optical deflection array, imaging apparatus, and image projection display apparatus
US20040263936A1 (en) * 2003-04-15 2004-12-30 Takeshi Nanjyo Optical deflection apparatus and manufacturing method thereof, optical deflection array, imaging apparatus, and image projection display apparatus
US8508436B2 (en) 2005-09-28 2013-08-13 Intellectual Properties | Kft Electronic display systems

Also Published As

Publication number Publication date
IT1101905B (it) 1985-10-07
IT7847511A0 (it) 1978-01-03
JPS53111292A (en) 1978-09-28
FR2376477A1 (fr) 1978-07-28
FR2376477B1 (fr) 1981-06-19
DE2800341A1 (de) 1978-07-13
GB1593011A (en) 1981-07-15

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